Novel Acute Retinal Artery Ischemia and Reperfusion Model in Nonhuman Primates

BACKGROUND AND PURPOSE

The retina, as an externally located neural tissue, offers unique advantages in investigating the effect of therapeutic intervention on the brain. In this study, we put forth a clinically relevant model of retinal ischemia and reperfusion in nonhuman primates.

METHODS

Acute retinal artery ischemia and reperfusion was induced by injecting an autologous clot into the ophthalmic artery of adult rhesus monkeys, and recanalization was achieved by focal thrombolysis with tPA (tissue-type plasminogen activator). Digital subtraction angiography and fluorescein angiography were used to evaluate blood flow in the retina and the choroid. Electroretinogram, optical coherence tomography, and hematoxylin and eosin staining were used to evaluate the structure and function of the retina after ischemia.

RESULTS

Digital subtraction angiography and fluorescein angiography images confirmed occlusion of the ophthalmic and central retinal arteries, as well as recanalization after tPA thrombolysis. Electroretinogram indicated retinal functional damage following ischemia, and thrombolysis partially rescued its impairment. Optical coherence tomography and hematoxylin and eosin staining revealed ischemia-induced changes in the retina, and tPA partially mitigated these damages.

CONCLUSIONS

This novel acute retinal artery ischemia and reperfusion model in rhesus monkeys may closely simulate retinal ischemia/reperfusion in clinical practice and provide an optimal platform for screening neuroprotective strategies.

Combined Surgical Ablation and Intravitreal Triamcinolone Acetonide for Retinal Angiomatous Proliferation

Purpose

Neovascular age-related macular degeneration (ARMD) with retinal angiomatous proliferation (RAP) has a poor natural history and the efficacy of any treatment has not yet been established. The authors describe a combined surgical treatment.

Methods

A 76-year-old woman presented with a best-corrected visual acuity (BCVA) of 20/600 in the right eye and macula with stage 3 RAP as identified by fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT). After a standard three-port pars plana core vitrectomy (PPV), endodiathermy of the arteriolar and venous feeder vessels of each lesion was performed, intraretinal RAP feeder vessels were cut with manual vertical intraocular scissors, and 0.1 mL of triamcinolone acetonide (TAAC) was injected intravitreally At 1 and 4 weeks and at the sixth month, the patient underwent a complete eye examination, FA, ICGA, and OCT to assess outcomes and complications.

Results

Six months later, BCVA was stable at 20/300, intraocular pressure was 15 mmHg, anterior segment and vitreous cavity were clear without evidence of TAAC granules, and retina was attached. FA and ICGA showed a complete occlusion of the RAP and absence of leakage or ischemia and OCT demonstrated decreased macular thickness with resolution of both intraretinal edema and pigment epithelium detachment, and the restoration of the normal macular profile. At the end of follow-up, the authors did not observe any ocular or systemic complication.

Conclusions

Surgical approach to RAP stage 3 with intravitreal injection of 4 mg of TAAC was safe and anatomically effective.

Angiography with a multifunctional line scanning ophthalmoscope

A multifunctional line scanning ophthalmoscope (mLSO) was designed, constructed, and tested on human subjects. The mLSO could sequentially acquire wide-field, confocal, near-infrared reflectance, fluorescein angiography (FA), and indocyanine green angiography (ICGA) retinal images. The system also included a retinal tracker (RT) and a photodynamic therapy laser treatment port. The mLSO was tested in a pilot clinical study on human subjects with and without retinal disease. The instrument exhibited robust retinal tracking and high-contrast line scanning imaging. The FA and ICGA angiograms showed a similar appearance of hyper- and hypo-pigmented disease features and a nearly equivalent resolution of fine capillaries compared to a commercial flood-illumination fundus imager. An mLSO-based platform will enable researchers and clinicians to image human and animal eyes with a variety of modalities and deliver therapeutic beams from a single automated interface. This approach has the potential to improve patient comfort and reduce imaging session times, allowing clinicians to better diagnose, plan, and conduct patient procedures with improved outcomes.

Improving the therapeutic window of retinal photocoagulation by spatial and temporal modulation of the laser beam

Decreasing the pulse duration helps confine damage, shorten treatment time, and minimize pain during retinal photocoagulation. However, the safe therapeutic window (TW), the ratio of threshold powers for thermomechanical rupture of Bruch's membrane and mild coagulation, also decreases with shorter exposures. Two potential approaches toward increasing TW are investigated: (a) decreasing the central irradiance of the laser beam and (b) temporally modulating the pulse. An annular beam with adjustable central irradiance was created by coupling a 532-nm laser into a 200-μm core multimode optical fiber at a 4-7 deg angle to normal incidence. Pulse shapes were optimized using a computational model, and a waveform generator was used to drive a PASCAL photocoagulator (532 nm), producing modulated laser pulses. Acute thresholds for mild coagulation and rupture were measured in Dutch-Belted rabbit in vivo with an annular beam (154-163 μm retinal diameter) and modulated pulse (132 μm, uniform irradiance "flat-top" beam) with 2-50 ms pulse durations. Thresholds with conventional constant-power pulse and a flat-top beam were also determined. Both annular beam and modulated pulse provided a 28% increase in TW at 10-ms duration, affording the same TW as 20-ms pulses with conventional parameters.

Microsurgical anatomy of the central retinal artery

OBJECTIVE

To define the microsurgical anatomy of the central retinal artery (CRA) and to provide a guide to avoiding damage to it during surgery.

METHODS

The anatomic characteristics of the CRA and small arteries distributed to the optic sheath were examined in 109 orbits. The origin, course, and site of entry of the artery into the optic sheath and the distance between the orbital apex and the site of entry into the sheath were examined.

RESULTS

The CRAs originated directly from the intraorbital ophthalmic artery or in a common trunk with a posterior ciliary or a muscular branch. The CRAs most commonly originated on the inferomedial side of the ophthalmic artery an average of 8.4 mm distal to the orbital end of the optic canal. They penetrated the optic sheath near the junction of the middle and anterior thirds of the length of the intraorbital optic nerve an average of 18.6 mm distal to the optic canal. More than 70% of CRAs penetrated near the midline of the lower surface of the optic sheath, 21% entered the inferomedial surface, and 7% the inferolateral or lateral surface of the optic sheath. Only one CRA gave off a branch before penetrating the nerve.

CONCLUSION

The CRA is at risk of being damaged or occluded during procedures involving a large part of the orbit. Procedures directed along the lower half of the proximal two-thirds of the optic sheath have the greatest risk of interrupting the artery.

Arterio-venous dissection after isovolaemic haemodilution in branch retinal vein occlusion: a non-randomised prospective study

PURPOSE

The rationale for this pilot study was to add arterio-venous dissection (AVD) after unsuccessful medical treatment in a well-defined group of patients with branch retinal vein occlusion (BRVO).

METHODS

In this prospective, interventional case series 35 consecutive patients with a visual acuity (VA) of 0.4 (logMar) or worse were scheduled for surgery within the first 3 months of the onset of BRVO. The study endpoint was VA 1 year after AVD. Secondary study endpoints were: correlation of VA and successful vessel dissection; complication rate; and number of additional surgical procedures within the first year of AVD.

RESULTS

Preoperative VA (logMar) was 0.82+/-0.05 (range 0.2-1.6). VA 6 weeks postoperatively was 0.54+/-0.06 (range 0-1.6), 3 months postoperatively 0.61+/-0.07 (0-1.56), 6 months postoperatively 0.74+/-0.08 (range 0-2) and 12 months postoperatively 0.55+/-0.07 (range 0.1-1.5). VA improved 1 year after AVD (p=0.0004). An improvement in VA did not depend on successful separation of the artery and the vein. Four patients had a retinal detachment, 19 patients needed cataract surgery within the first year of AVD. A total of 24 additional surgical procedures were needed.

CONCLUSIONS

Patients with BRVO may profit from AVD compared with a historical control group. Visual improvement was found irrespective of the successful dissection of vessels. The cataract formation rate and additional surgery was a shortcoming of the AVD procedure.

[Surgical approach to retinal vein occlusion]

Retinal vein occlusions are the second most common vision threatening retinal vascular disorders. Our therapeutic armamentarium for functional improvement was very limited in the past for all types of retinal vein occlusions (branch, central and hemi-central retinal vein occlusion). Also pathomechanism and risk factors are not completely understood yet. Argon-laser-photocoagulation can prevent the development and treat neovascularizations successfully, but is unable to improve visual function in most cases. Thrombolytic therapy applied systemically is limited due to serious side effects but may be helpful when injected intraocularly. Isovolemic hemodilution may be efficacious in central retinal vein occlusion (CRVO). The creation of a laser-induced chorioretinal venous anastomosis showed serious complications. Since 1999 numerous reports on successful surgical techniques were published. It could be shown that the dissection of the adventitial sheath with separation of the artery from the vein at the arteriovenous crossing where branch retinal vein occlusion occurs can re-establish the retinal blood flow with reduction of macular edema. But it is still unclear which step of the surgery (vitrectomy, ILM-peeling, sheathotomy) is causative for the results. A new surgical approach in CRVO is the radial optic neurotomy (RON). This technique was primarily performed under the hypothesis of decompression of the central vein by cutting the scleral ring. Meanwhile there is some evidence that the formation of chorioretinal shunts may be the decisive factor in cases of successfully performed RON. Due to inconsistent and rare data this surgical procedure needs further evaluation. Another surgical option is the cannulation of the occluded vein. This technique seems to be feasible but the clinical results still have to be proved. Despite several uncertainties and open questions, surgical techniques are likely to overcome the desolate therapeutic situation for retinal vein occlusion of the past.

Treatment of an avulsed retinal vessel with infrared diode laser photocoagulation

PURPOSE

To report the use of the infrared diode laser with long-duration pulses to successfully treat a patient with recurrent vitreous hemorrhages due to an avulsed retinal arteriole.

DESIGN

Interventional case report.

METHODS

A 70-year-old man presented with repeated, visually significant vitreous hemorrhages due to an avulsed retinal arteriole. Infrared diode laser photocoagulation with long-duration, large, overlapping spots was performed on either side of the avulsed segment.

RESULTS

Resolution of the hemorrhage occurred within 1 month, without further episodes of bleeding. Two-year follow-up with fluorescein angiography showed complete cessation of blood flow through the treated segment.

CONCLUSIONS

Infrared diode laser photocoagulation with long-duration pulses may be an effective, minimally invasive treatment of the avulsed retinal vessel syndrome.

Argon laser photocoagulation for the treatment of idiopathic, bilateral, recurrent, diffuse retinal arterial aneurysms

Spontaneous resolution of retinal arterial aneurysms may occur, but recurrences are uncommon. A case of idiopathic, bilateral, recurrent, diffuse retinal arterial aneurysms treated with direct laser photocoagulation is described. A 30-year-old woman with a history of physiologic menopause was found to have bilateral, diffuse, multiple retinal arterial aneurysms with massive subretinal exudates and intraretinal hemorrhages. Fluorescein angiography demonstrated multiple retinal arterial aneurysms with leakage. Direct argon laser photocoagulation successfully closed the aneurysms. During 6 years of follow-up, the aneurysms reoccurred twice, coinciding with a postpartum period. Recurrences were successfully treated with repeated laser photocoagulation with the aneurysms closed off. Hormonal imbalance may play a role in this condition. Recurrent retinal arterial aneurysms can be managed by direct laser photocoagulation.

Preliminary clinical observation of arteriovenous sheathotomy for treatment of branch retinal vein occlusion

PURPOSE

To document the anatomic and functional improvement of six patients with branch retinal vein occlusion (BRVO) following successful arteriovenous adventitial sheathotomy (AAS).

METHODS

Retrospective study of 6 patients (6 eyes) with BRVO treated with AAS. All patients were not eligible for laser photocoagulation and had both macular edema and intraretinal hemorrhage. The visual acuity was in the range of 0.4 to 0.02. All patients underwent pars plana vitrectomy and AAS. The clinical improvement was determined by fundus photograph, fluorescein angiography (FAG), optical coherence tomography (OCT) and multifocal electroretinography (ERG). All patients were followed postoperatively for an average of 20 months ranging from 12 to 24 months.

RESULTS

Sheathotomy and decompression of the arteriole/venule (A/V) crossing were achieved in all 6 patients. 5 patients have improved their best-corrected visual acuity 4 lines or more. The best one could reach to 1.0. One month after the operation, fundus photograph and FAG demonstrated the resolution of intraretinal hemorrhage, reduction of non-perfusion area and apparent resolution of retinal venous dilation and tortuosity. OCT confirmed remarkable reduction of retinal thickness. The microcysts at the fovea diminished. Multifocal ERG showed the recovery of the central peak at the macular and the peripheral response density. However, capillary nonperfusion area and microaneurysm were found out by FAG in four patients at the points distal to the sheathotomy three months after the operation.

CONCLUSIONS

Anatomic and functional improvement of retina can be achieved in patients with BRVO through AAS. However, the capillary nonperfusion and microaneurysm may follow this surgical procedure in some cases that need further treatment with laser photocoagulation. The better visual improvement may be expected in the patients with earlier surgical intervention.

Vitrectomy with arteriovenous decompression and internal limiting membrane dissection in branch retinal vein occlusion

PURPOSE

The therapeutic armamentarium for functional improvement after branch retinal vein occlusion (BRVO) is limited with uncertain efficacy. Some surgeons have proposed surgical decompression of the vein at the arteriovenous (AV) crossing.

METHODS

Forty-three patients with BRVO were treated in the authors' department from August 1999 to April 2001 with AV decompression. Twenty-five patients with comparable BRVO who refused this surgical intervention served as a control group. All 68 patients received an isovolemic hemodilution therapy for 10 days. The surgical procedure consisted of a standard pars plana vitrectomy and separation of the overlying artery from the vein using microscissors. In 16 cases dissection of the internal limiting membrane (ILM) in the macular area and around the AV crossing was also performed. Assessment of visual acuity, fluorescein angiography, and multifocal electroretinography were performed preoperatively and 6 weeks after surgery in seven patients.

RESULTS

Surgical procedure and postoperative course were uneventful. In most of the treated eyes visual acuity improved and fluorescein angiography revealed capillary reperfusion. Functional results in patients with AV decompression were highly significantly better than in the control group. Furthermore, removal of the ILM seems to have an additional beneficial effect on the functional outcome.

CONCLUSION

These results demonstrate the therapeutic effect of surgical AV decompression in BRVO. Additional removal of the ILM seems to improve the functional results. Further experience may answer some open questions.

Familial retinal arterial macroaneurysms

PURPOSE

To describe the salient clinical features and course of a new entity.

METHOD

Retrospective study of the clinical examinations, photographic and angiographic documentation, and clinical course of seven children from three unrelated Saudi families with multiple retinal arterial macroaneurysms.

RESULTS

There were four females and three males: one set of two sisters (patients 1 and 2), a brother and a sister (patients 3 and 4), and a sister and two brothers (patients 5, 6 and 7). The age at first symptoms ranged from 3 months to 19 years. The first four cases were labeled for many years as "atypical bilateral Coats." Each patient demonstrated the presence of beading and macroaneurysms along the major retinal arterial trunks bilaterally. In five patients, recurrent bleeding and leakage from these macroaneurysms occurred, resulting in visual loss. The blood was mainly located under the internal limiting membrane. It reabsorbed spontaneously in all patients, with improved visual acuity. In three patients, argon laser photocoagulation of leaking macroaneurysms was followed by clinical improvement. Follow-up ranged from 18 months to 17 years (average = 7.8 years).

CONCLUSION

The authors report, to the best of their knowledge, a new condition that they propose to call "familial retinal arterial macroaneurysms."

A ruptured retinal arterial macroaneurysm presenting as subhyaloid haemorrhage

We report a case of ruptured retinal arterial macroaneurysm with overlying subhyaloid haemorrhage. Both subhyaloid haemorrhage and subsequently the macroaneurysm was treated with argon laser photocoagulation.

Transretinal feeder vessel ligature in von Hippel-Lindau disease

PURPOSE

To present a new technique called transretinal feeder vessel ligature for the treatment of retinal angiomas.

METHODS

Case report of a patient with peripheral retinal angiomas previously treated unsuccessfully with photocoagulation who responded to this new, alternative surgical treatment.

RESULTS

The retinal angiomas decreased in size although two new feeder vessels appeared and the lesions showed a regression pattern after additional laser therapy over the vascular tumors.

CONCLUSIONS

A transretinal feeder vessel ligature in association with vitrectomy and photocoagulation may be useful for some advanced or non-responsive cases of retinal angiomas.

Arterial crimping in branch retinal vein occlusion with macular edema

PURPOSE

To evaluate the effects of arterial crimping plus grid pattern laser photocoagulation on the macular edema due to branch retinal vein occlusion.

PATIENTS AND METHODS

Seventy two eyes (70 patients) with macular edema due to BRVO were divided into two similar groups according to age, gender, location and extent of the occluded area. Grid pattern laser photocoagulation alone was applied in 34 eyes (group A), whereas arterial crimping plus grid pattern laser was used in 38 eyes (group B). Visual acuity, central 30 degree perimetry, and fundus fluorescein angiography were carried out in all patients at each examination. Patients were followed up for an average of 23 mo (ranging from 11 to 34 mo).

FINDINGS

A rate of 62% and 79% improvement in macular edema was recorded in groups A and B, respectively (p=0.057). The perimetric performance value improved more in group B than in group A (p=0.028). In addition, visual acuity improved more in group B than group A (p=0.041).

CONCLUSION

In patients with BRVO, grid pattern retinal photocoagulation treatment plus arterial crimping resulted in better visual performance two years after treatment than did grid pattern photocoagulation alone.

Expression of c-fos and c-jun mRNA following transient retinal ischemia: an approach using ligation of the retinal central artery in the rat

The expression of the proto-oncogenes c-fos and c-jun was examined by in situ hybridization at various timepoints following transient retinal ischemia by means of ligation of the retinal central artery in the rat. Ischemia of 90-minute duration resulted in the degeneration of neurons in both the ganglion cell layer and the inner nuclear layer at 48 hours after reperfusion. The expression of c-fos and c-jun messenger RNA throughout the entire inner nuclear layer was transiently coinduced following 90-minute retinal ischemia with a peak at 1 hour after reperfusion. This expression was also found in the ganglion cell layer at 3 hours after reperfusion. Weak signals for c-fos and c-jun mRNA were observed at 24 hours after reperfusion and returned to near control levels by 48 hours. c-jun protein expression was detected in the ganglion cell layer, the middle of the inner nuclear layer, and optic nerve head at 3 hours, but not 1 hour, after lethal ischemia/reperfusion; however, c-fos protein expression was not detected after reperfusion. Whereas no neuronal degenerative changes were found at 7 days after 30-minute ischemic retina, c-fos and c-jun messenger RNA were also induced at 1 hour postreperfusion. To our knowledge, this study is the first report to show expression patterns of immediate-early genes after retinal ischemia/reperfusion. These results suggest that changes in expression of c-fos and c-jun after transient retinal ischemia are similar to those after transient brain ischemia, and the selective occlusion of the central retinal artery will provide a useful model for studying ischemic neuronal degeneration in vivo in the rat retina.

[Online measurement of retinal artery branches in type II diabetic patients. Initial clinical trials before and after laser coagulation]

By the use of a new online measuring system the effect of argon-laser coagulation in diabetics on the diameters of retinal arteries was measured.

METHOD

The vessel diameter of retinal branch arteries were measured in patients with type-II diabetes before and after (0.5 h) argon-laser coagulation. Ten patients without previous laser treatment were included in this study. Measurements were taken in all four quadrants by the use of a new automatic online measuring system.

RESULTS

The new technique allowed measurements to be made within an acceptable period of time and with little strain on patients. After argon-laser coagulation 56.7% of retinal arteries showed a significant vasodilation. No significant changes in vessel diameter were found in 18.9% of these arteries, whereas 24.3% showed significant vasoconstriction.

CONCLUSION

The new online measuring system is able to measure the effects of photocoagulation on an individual basis with a noninvasive technique. The first findings presented here confirm previous studies of larger groups, with a considerable reduction in efforts required.

Imaging of chorioretinal anastomoses in vascularized retinal pigment epithelium detachments

OBJECTIVE

To identify specific features of pigment epithelium detachments with limited hyperfluorescent lesions (hot spots).

DESIGN

One hundred eighty-two consecutive patients (186 eyes) who had vascularized pigment epithelium detachments and recent onset of symptoms were examined with indocyanine green and fluorescein videoangiography using the scanning laser ophthalmoscope. The choroidal neovascularization complex and macular retinal vessels were studied. The natural history and the effect of laser treatment were evaluated.

RESULTS

Fifty-four eyes had hot spots on indocyanine green angiography. In 50 of these 54 eyes, the video analysis showed an anastomosis of one or more retinal vessels, with the choroidal neovascularization within the hot spot. One or two retinal veins or arteries or both filled with both dyes and were seen to enter into the hot spot. Results of indocyanine green-guided photocoagulation of the hot spot in 28 eyes were disappointing.

CONCLUSION

Continuous recording of the early phases of fluorescein and indocyanine green angiography allowed identification of chorioretinal anastomoses in vascularized pigment epithelium detachments with hot spots at an early exudative stage of age-related macular degeneration in 50 (26.8%) of 186 eyes. The poor outcome of laser photocoagulation could be related not only to the development of an overlying pigment epithelium detachment, but also to the retinal and choroidal vascularization of the lesion.

Capillary macroaneurysms in central retinal vein occlusion

The occurrence of macroaneurysms as a consequence of central retinal vein occlusion was previously reported in one study only with the appearance of a single capillary macroaneurysm. We report a case of central retinal vein occlusion presenting several capillary macroaneurysms. It may be supposed that retinal ischemia plays an important role in the pathogenesis of capillary macroaneurysms, in association with the pressure increase in the capillary network due to venous obstruction.

Retinal arteriolar macroaneurysms: long-term visual outcome

Visual outcome was analysed in 16 consecutive eyes with symptomatic retinal arteriolar macroaneurysms treated by direct laser photocoagulation and 26 consecutive symptomatic eyes followed with no treatment. No difference existed between groups in presenting visual acuity, macular involvement, presence of macular subretinal fluid, or presence or location of associated haemorrhage. The mean follow up was 41 months. In the 26 untreated eyes, visual acuity was improved by 2 or more lines in 13 (50%), was unchanged in nine (35%), and decreased in four cases (15%). In the 16 treated cases, three improved (19%), seven were unchanged (43%), and six had decreased visual acuity (38%). The average minimum angle of resolution improved 0.53 log units in untreated cases and decreased 0.14 log units in treated cases (p = 0.02). Multivariable logistic regression modelling analysis revealed that laser treatment remained a significant risk factor for final visual acuity of less than 20/80 even when controlling for the effects of subretinal haemorrhage and foveal subretinal fluid (odds ratio 8.4, p = 0.01). Laser photocoagulation directly to the macroaneurysm did not improve the visual outcome in this series.

Congenital arteriovenous communications and the development of two types of leaking retinal macroaneurysms

We treated a patient with a rare combination of congenital arteriovenous communications and the development of leaking macroaneurysms of different types. Initially, leaking macroaneurysms developed in the shunt area of the arteriovenous communication; later, a preexistent fusiform macroaneurysm in the afferent arteriole of the congenital communication started leaking. Because exudates and fluid from the leaking macroaneurysms reached the fovea, laser treatment was performed to obliterate the macroaneurysms. We assume that after obliteration of the macroaneurysms with laser in the shunt area, the increase of hydrostatic pressure on the thin wall of the fusiform aneurysm of the afferent artery led to its leaking. We saw no signs of vascular occlusion after laser treatment.

Coats' disease

Coats' disease is an ocular condition characterized by telangiectatic vessels, microaneurysms, and intraretinal and subretinal exudates. This disease entity is usually uniocular, occurs in young males in their first decade of life, and has a prevalence for the temporal retina. A case report of Coats' disease is presented along with a discussion of its management and treatment.

Surgical decompression of branch retinal vein occlusions

Many patients with branch retinal vein occlusions can develop significant long-term diminution of vision due to such complications as macular edema, retinal neovascularization, and vitreous hemorrhage. One of us (S.C.) developed a new surgical procedure that involves sectioning or decompression of the common sheath connecting the artery and vein at the crossing where a branch retinal vein occlusion occurs. The patient whose case we report had a visual acuity improvement from 20/200-2 to 20/25+1 eight months after surgery.

Purulent anterior segment endophthalmitis following paracentesis

A 67-year-old man developed a central retinal artery occlusion and was treated with an oral carbonic anhydrase inhibitor, oral glycerin, carbachol rebreathing, and anterior chamber paracentesis. He subsequently developed an anterior segment endophthalmitis. Vigorous medical and surgical management cured the endophthalmitis, but his visual acuity remained at light perception. To the best of our knowledge, this patient represents the first reported case of a culture-positive, anterior segment endophthalmitis following anterior chamber paracentesis.

[Reversible star formation of the macula in retinal angiomatosis]

Case report concerning a young man in whom exudative retinitis had occurred as a result of the A-V shunt of a retinal angioma, leading to sudden loss of vision. With argon laser and xenon arc photocoagulation a minor hemorrhage cleared up spontaneously, the retina remained attached and vision increased to 20/25 within 1 year. The authors believe that the combined photocoagulation insured an interruption of blood flow in feeder vessels and the breakdown of the intervening capillary bed.

Retinal vessel photocoagulation: a quantitative comparison of argon and krypton laser

Retinal arteries of owl monkeys were photocoagulated with single exposures to argon laser green light (514 nm), krypton laser green light (531 nm), and krypton laser yellow light (568 nm). The distribution of damage along the vessel in different retinal layers was characterized geometrically after serial sectioning of the histopathologic material. Krypton laser radiation (green and, to an even greater extent, yellow) produced measurably greater effects on retinal vessels and adjacent structures than on deeper retinal levels; argon laser radiation (green) produced greater effects on the pigment epithelium. Krypton yellow produced the greatest total effect. The location of damage to the retinal arteries and pigment epithelium differed, with the peak of the damage around the arteries being farther from the optic disc than was the peak of the pigment epithelial damage.

Acquired macroaneurysms of the retinal arteries

Acquired macroaneurysms of the retinal arteries are rather frequent. Four new cases are reported. Aetiology, clinical features, fluorescein angiographic aspects, complications, prognosis, pathogenesis, differential diagnosis and treatment by photocoagulation are discussed.

Chorioretinal vascular anastomoses after perforating trauma to the eye

A 32-year-old white man sustained an ocular injury with a small piece of metal. He had perforation of the retina and choroid, and later developed chorioretinal vascular anastomosis. Disabling complications, such as neovascular growth, serous transudation, or hemorrhages, did not occur within a ten-month follow-up period. Interruption of Bruch's membrane and the retinal pigment epithelium, with approximation of the normally separated vasculatures of the choroid and retina, appears necessary for such anastomoses to occur.

Optic nerve circulation and ocular pressure: contribution of central retinal artery and short posterior ciliary arteries and the effect on oxygen tension

Blood-flow rate in the optic nerve of the rhesus monkey 4 mm. behind the globe monitored by the heated thermocouple and tissue p02 measurement is found to be influenced by ocular pressure level. Ligation of central retinal artery reduced flow rate to 79 per cent of normal but did not influence the effect of IOP on blood-flow rate. Ligation of short posterior ciliary arteries reduced blood-flow rate to 21 per cent of normal and virtually eliminated the IOP effect. Raising IOP to above systolic arterial pressure level reduced blood-flow rate to 17 per cent of normal. At IOP levels greater than 50 mm. Hg, the reduction in blood-flow rate and in Po becomes marked and may be sufficient to produce primary lesions at this site.